Silver halide emulsions for the production of reversal colorphotographic images

ABSTRACT

A silver halide emulsion mixture for the preparation of colorphotographic reversal images by the imagewise exposure and color development of red- green- and blue sensitive emulsion layers in at least one of which the emulsion is a mixture of a relatively highly sensitive silver halide and a relatively less sensitive silver halide emulsion wherein the less sensitive silver halide emulsion has an average grain size at least 50 percent of the average grain size of the more highly sensitive emulsion.

I United States Patent 1 1 7 9,764 Moll et al. Dec. 18, 1973 1 SILVER I-IALIDE EMULSIONS FOR THE [58] Field of Search ..96/59. 68, 94, 74

PRODUCTION OF REVERSAL COLORPHOTOGRAPHIC IMAGES [56] References Cited [75] lnventors: Ftraziz llvlolt; Berigard hilzorclllier, both UNn-ED STATES PATENTS 0 0e namm elm; ric Reckziegel, Leverkusen; Wilheim 3,600,180 8/1971 Judd et al. 96/94 Saleck, I I Schildgen-Bergisch-Gladbach, all of Pnmary Q w f Germany Assistant E.\'ammerRrchard L. Schilling Armrne vArthur G. Connolly et al. [73] Assignee: AGFA-Gevaert AG, Leverkusen,

Germany v [57] ABSTRACT [22] Filed: Nov. 10, I971 i 1 A s|lver halide emulsion mixture for the preparation of pp .1 197,480 colorphotographic reversal images by the imagewise Re'ated Us. Application Data exposure and color development of redgreenand blue sensitive emulsion layers in at least one of which [63] Continuation of Ser. No. 781,832, Dec. 6, 1968, the emulsion IS a mixture of a relatively highly sensiabandoned.

tive silver halide and a relatively less sensitive silver [30] Foreign Application Priority Data halide emulsion wherein the less sensitive silver halide emulsion has an average gram size at least 50 percent Dec. 6, I963 Germany P [5 97 506.1 of the average grain Size of the more sensitive I 52 us. Cl. 96/59, 96/74 R, 96/94 R [5 1] Int. Cl G03c 5/50 2 Claims, 4 Drawing Figures PAIENTEUBEBI 8 ma 3,779,764

SHEET 3 BF 3 SILVER HALIDE EMULSIONS FOR THE PRODUCTION OF REVERSAL COLORPHOTOGRAPHIC IMAGES This application is a continuation of the co-pending prior U. S. application Ser. No. 781,832 filed Dec. 6, 1968, now abandoned.

This invention relates to a process for the production of silver halide gelatine emulsions for use in colorphotographic reversal films which yield a positive colorphotographic image upon exposure and development in developers which contain thiocyanates.

The more sensitive a light sensitive photographic material, the coarser will be the grain of the photographic material. Thus, for example a film which has a sensitivity of DIN is not unduly grainy at a magnification of 15 times magnification whereas a film of 27 DIN shows coarse grain structuresat magnification above 6. This property of photographic materials is not only observed in black-white materials but applies equally to colorphotographic materials. This coarsening of the grain with the increase in sensitivity is based on the necessity to increase "the silver halide grain in high speed emulsions.

To adjust the photographic properties such as the gamma value of the individual silver halide layers, mixtures of different silver halide emulsions are generally employed in colorphotographic reversal materials. These may, for example, consist of a high speed emulsion, an emulsion of medium speed and a low speed emulsion. The proportions of the individual emulsions which are used can be varied within wide limits depending on the photographic properties of the individual emulsions and on the effects desired. Since in practice the quality of color-photographic reversal materials often suffers from too steep a gamma of the silver halide emulsion in the individual layers, the gamma and, in particular the speed relationship of the emulsion components, must be adjusted so that the gammavalues will be in the region of about 1.4 to 1.7. To achieve this it is necessary that the difference in sensitivity between the low sensitive emulsion and the high speed emulsion has a certain value. Previously attempts have been made to improve the grain of the final dye image by using as far as possible fine grained silver halide emulsions for the low speed emulsion while maintaining the required total speed for the desired gamma value. The measures which have been employed, however, were not satisfactory in practice.

It is among the objects of this invention to improve the speed to grain size relationship of photographic silver halide emulsions, i. e. to obtain the finest possible dye grain with the highest possible speed of the silver halide emulsion.

We now have found that the granularity of colorphotographic images which are produced by the color reversal process and in which the first development (black-white development) is carried out in the presence of thiocyanate ions can be greately improved by using emulsion mixtures of at least one emulsion of higher speed with another silver halide emulsion having lower speed for the silver halide emulsions in the individual layers but, in contrast to the measures previously used, using for the low speed emulsion, while maintaining substantially the same sensitivity in proportion to the high speed emulsion, an emulsion which has been made as coarse grained as possible by increased physical ripening and reduced chemical ripening. The average grain size of the less sensitive or low speed silver halide emulsion should be at least 50 percent and preferably 50 to percent of that of the high speed emulsion. This measure is not confined to mixtures of two emulsions but also applied to mixtures of several emulsions.

The effect of the invention is extremely unexpected since it has previously been assumed that the grain granularity of the image dye can only be improved by using finer grained silver halide emulsions. For this reason, the average grain size of the less sensitive emulsions used in the previously known silver halide emulsion mixtures for color reversal materials was generally only about 20 to 30 percent of that of the more sensitive emulsion. For the same reasons, there was a tendency to use even smaller average grain sizes.

The preparation of the emulsions which are used according to the invention are described e. g. in Glafkides Photographic Chemistry, Vol. 1, pages 298 et seq Fountain Press, London 1958. The procedure employed may, for example, be as follows.

A silver nitrate solution is added over a given time at a predetermined temperature to a gelatine solution which contains potassium iodide and potassium bromide. Potassium bromide is used in excess so that the so-called physical ripening i. e. the increase in the large silver halide crystals at the expense of the smaller grains, can take place by complex formation with the silver halide already formed. The physical ripening starts as soon as silver nitrate is added -to the aqueous alkali metal halide solution. It can be assisted by occasionally interrupting the addition of silver nitrate solution into the precipitation mixture. The physical ripening is carried out at temperatures of between 45 to 70C.

The physical ripening can be controlled by varying the temperature. A higher temperature produces increased physical ripening due to greater complex formation and hence results in a coarser grain and higher speed.

Other methods for obtaining a coarser grain structure consist, for example, in the addition of a silver halide solvent, e. g. ammonia or by using a more concentrated reaction mixture, which is equivalent to increasing the bromine ion concentration, or by using an increased quantity of gelatine when preparing the mixture.

Silver halide emulsions of this type yield a finer dye grain if processed in accordance with a color reversal process including black-white development in a thiocyanate-containing developer than silver halide emulsions which have been ripened at lower temperatures under otherwise the same conditions and which have a smaller average grain size.

The sensitivity of the coarser silver halide emulsion prepared according to the invention is higher. This can be corrected by modifying the chemical ripening, or by using certain kinds of gelatine or by changing the pH or pAg value. Further more it is possible to add certain ingredients which decrease the the sensitivity.

Stabilizers may also be added to the emulsion in such quantities that the sensitivity is reduced by the required amount. Stabilizers of this type are, for example, mercury compounds, palladium compounds, rhodium compounds and osmium compounds.

Apart from these stabilizers, at the after-ripening stage the usual sulfur compounds, gold salts and if desired onium salts for chemical sensitization are added to the emulsion. The quantity of gold salt added may also be varied to reduce the sensitivity or the gold may even be omitted completely. As to details regarding the gold sensitization we refer to the book by R. Koslowski, Z. wiss. Phot. 46, 65 72 (1959).

The emulsions may also be optically sensitized, e. g. with the usual polymethine dyes such as neutrocyanines, basic or acid carbocyanines, rhodacyanines, hemicyanines, styryl dyes, oxonoles and the like. Such sensitizers have been described in F. M. Hamer The Cyanine Dyes and related Compounds (1964). For suitable color couplers. reference may be made to the chapter dealing with this subject in the book mentioned above by Glafltides.

The emulsions which have been after-ripened are mixed with other silver halide emulsions to obtain the desired gamma-value and speed. Thereafter the usual casting additives such as stabilizers against fogging on storage, hardening agents, plasticizers, bactericidal agents and wetting agents are also added.

EXAMPLE 1 A silver halide gelatine emulsion mixture for the red sensitive emulsion layer of a three-layered colorphotographic reversal material, which emulsion layer contains a cyan color coupler, is prepared as follows:

The more sensitive emulsion is a silver iodobromide gelatine emulsion which has been prepared in the usual manner and which has an iodine content of 6 mols per cent This emulsion has a relatively coarse grain owing to its sensitivity. The result of a sedimentation analysis which is representative for the grain size distribution is shown by curve I in FIG. 1. In this diagram, the axis of ordinates represents the grain size in am and the axis of abscissas the residue in percent. The average grain size of this emulsion is about 0.76

The grain distribution was determined by means of the known sedimentation analysis (see e. g. VDI Zeitschrift, Volume 109, No. 17 pages 757 et seq.).

The above emulsion was divided into two parts.

Part A 40 parts by weight ofa less sensitive silver halide gelatine emulsion 3 (curve 3 of FIG. 1) was added to 60 parts by weight of the above high-speed emulsion 1.

Emulsion 3 is a silver iodobromide gelatine emulsion which has an iodide content of 8 mols per cent, which was prepared in the usual manner.

The time for physical ripening (addition of precipitation components plus interruptions) amounts to 27 minutes, the precipitation temperature 65C. When finished, emulsion 3 has the grain distribution represented by curve 3 in FIG. 1, 50 percent of the grains being larger than 0.32 p. up to a maximum of 0.8 p. and 50 percent of the grains being smaller than 0.32 a down to a minimum of 0.95 1,.

Part B (Comparison test) 40 parts by weight of the less sensitive silver iodobromide gelatine emulsion 2 (curve 2 of FIG. 1) are also added to parts by weight of the above high-speed 60 sented by curve 2 in FIG. 1. It is found that 50 percent of the grains are large 1111.50.44 p. up to a maximum of 0.95 ,u. and 50 percent of the grains were smaller than 0.4 4 ,u. down to a minimum of 0.09 a.

Due to the more intensive ripening emulsion 2 is more sensitive than emulsion 3.6 mg of palladium ammonium chloride per kg of emulsion were added to emulsion 2 in order to reduce the sensitivity to that of emulsion 3.

Emulsion mixtures A and B are processed in the same mannersThe following additives are first added per litre to the emulsions:

50 ml of a 1 percent methanolic solution of 4-hydroxy-6-methyl-l,3, 3a, 7-tetrauzaindene.

22 g of cyan coupler of the following formula 0 ONHQCnHu 8 ml ofa 5 percent aqueous solution of chromium acetate as hardener, and

25 ml of a 7.5 percent aqueous solution of saponin as wetting agent.

The emulsions are then applied on to a support of cellulose acetate and dried.

It is exposed in a sensitometer customarily employed in the art behind a grey test wedge and thereafter processed as follows 2 1. Black-white development, 20 minutes at 20C.

3 g p-methy1aminophenol 6 g hydroquinone 50 g soda (anhydrous) 20 g sodium sulfite (anhydrous) 2 g potassium thiocyanate 2 g potassium bromide l aeaat stanhes a g--- make up to 1 lwith water, pH 10.8

10 ml acetic acid 20 g sodium acetate make up to 1 1 with water 3. Rinsing 10 minutes 4. Second uniform exposure 5. Color development. 14 minutes 20%.

5 g N,N-diethyl-p-phenylenediamino hydrogen sulfate 1.2 g hydroxyl ammonium sulfate 5 g sodium sulfite (anhydrous) 75 g potash 2 g potassium bromide 5 ml ethylene diamine 2 g hexametaphosphate make up to l 1 with water 6. Stop bath, 5 minutes 10 ml acetic acid 20 g sodium acetate make up to l l with water 7. Rinsing 5 minutes 8. Bleaching bath I g potassium ferricyanide water up to l l 9. RinsingS minutes 10. Fixing minutes 200 g sodium thiosulfate water up to l l 11. Final rinsing minutes.

A cyan step wedge is obtained in both cases. The dye grain of the cyan image is then measured for both samples by determining the Wiener spectrum.

The wiener spectrum W gives information on the noise energy and its frequency distribution of statistically distributed events. In the case of photographic dye grains W indicates the magnitude of the noise energy (fluctuations in density) and how these grain sizes (lines per mm) are distributed.

Measurement of the Wiener spectrum is described in The Measurement of power spectra R. B. Blackman and J. W. Turkey, Dover Publications, Inc. New York and Agfa Mitteilungen Volume II, E. Zeitler, p. 217 and H. Frieser p. 249.

The curves obtained with the emulsion are shown in FIG. 2. In this diagram, the local frequency spectrum of the grain is plotted along the abscissa and the square root of the noise energy along the ordinate. The steep rise w of sample A indicates a high proportion of coarse dye grains. Conversely, the flatness of the curve of the emulsion mixture B indicates a much finer grain of the image dye. It is found that the noise energy of emulsion mixture B is only about one-fourth of that of emulsion The comparison test proves that a much finer grained dye image is obtained although a coarser grained silver halide emulsion mixture is used as the starting material.

EXAMPLE 2 A high-speed silver iodobromide gelatine emulsion which has anieisl sgnt n Q ..4.PQFSQH. isate i9 the usual manner. This emulsion is relatively coarse grained. The grain size distribution as the result of a sedimentation analysis as described in Example 1 is shown by curve 4 of FIG. 3. In the diagram the grain size in pm is plotted along the axis of abscissa against the residue in percent along the axis of ordinates.

This emulsion serves as the more sensitive component for the preparation of an emulsion mixture for the green sensitive layer, which contains a magenta color coupler, of a color reversal material.

The above emulsion is divided into two parts C and D. These two parts are treated as follows:

Part C 60 parts by weight of a less sensitive silver iodobromide gelatine emulsion 6 (silver iodide content 4 mol.-%) are added to 40 parts by weight of the above emulsion 4. The total time for the physical ripening of the emulsion 6 was minutes. The temperature was 50C. The grain size distribution of emulsion 6 is represented by curve 6 in FIG. 3. 50 percent of the silver halide grains of this emulsion have a'grain diameter of more than 0.18 p.. This emulsion is then chemically ripened by the addition of sulfur ripening accelerators and gold salts.

Part D Y 60 parts by weight of a less sensitive silveriodo bromide gelatine emulsion 5 are added to 40 parts by weight of the above high-speed silver iodobromide emulsion 4. Emulsion 5 has the same silver halide composition as emulsion 6 but has been longer physically ripened. The time of physical ripening was 24 minutes at the same temperature. The grain size distribution of this emulsion is represented by curve 5 of FIG. 3. 50 percent of the grains have a diameter of more than 0.3 11.. The emulsion is chemically ripened in the same way as emulsion 6 but without the addition of gold salts. The same sensitivity as in emulsion 6 is thereby obtained in spite of the coarser grain.

Parts C and D are further treated in the same manner, employing substantially the same procedure as in Example 1. Instead of the red sens itizer, mg. of the green sensitizer of the following formula:

iii?

are added and instead of the cyan coupler, 18 g. of the magenta color coupler of the following formula per kg. of emulsion l. A process for the preparation of color photographic reversal images in a multi-layered color photographic reversal material which comprises:

a. imagewise exposing a multi-layered color photographic material which contains the following:

i. a red sensitive silver halide emulsion layer with a cyan color coupler capable of reacting with the oxidation product of a color-forming developer to yield a cyan dye,

ii. a green sensitive silver halide emulsion layer with a magenta coupler and iii. a blue sensitive silver halide emulsion layer with a yellow color coupler;

b. black-white developing said exposed photographic multi-layered material with a black and white developer which contains thiocyanate ions;

c. a second uniform exposing and developing of a said exposed and developed photographic multilayered material, and d. rinsing and fixing the exposed and developed multi-layered material, wherein the improvement comprises at least one of the silver halide emulsion layers consisting of a mixture of at least two silver halide emulsions each containing regular silver halide grains and having different sensitivities wherein the average grain size of the less sensitive silver halide emulsion is at least 50 percent of that of the more highly sensitive emulsion and the spectral sensitivity of the two mixed emulsions being substantially the same. 2. The process of claim 1, wherein the average grain size of the less sensitive silver halide emulsion is 50 to percent of that of the more highly sensitive silver halide emulsion.

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,779,76 Dated D c- 1973 Inventor(s) Franz M011 e1: 81

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, 1ine58, cancel "greately" and insert greatly Column 2, line 59, cancel "the" (second occurrence). Column 3, line 30, after "cent" insert a period.

Column 3, line 62, after "3" insert a period.

Signed and sealed this 18th day of June 1971;.

(SEAL) Attest: I V EDWARD 'MJLE'ICHEL'JR. c. MARSHALL mm Attesting Officer I Commissioner of Patents FQRM 504050 i I I uscoMM-m: seen-Poe 2 a ,5. GOVERNMENT PRINT'NG OFFICE t I989 0-365735, 

2. The process of claim 1, wherein the average grain size of the less sensitive silver halide emulsion is 50 to 70 percent of that of the more highly sensitive silver halide emulsion. 